关键词: S/Se co-filling, skutterudites, thermoelectric materials, high-temperature and high-pressure

Abstract: Although n-type skutterudites modified by electropositive fillers have been extensively studied, research on p-type skutterudites filled with electronegative elements remains scarce. In this work, a series of sulfur/selenium (S/Se) co-filled and iron (Fe)-doped p-type skutterudite samples with a nominal composition of S$_{0.1-x}$Se$_{x}$Fe$_{0.2}$Co$_{3.8}$Sb$_{12}$ ($x= 0.025$, 0.05, 0.075, 0.1) were rapidly synthesized via the high-temperature and high-pressure (HPHT) technique. Phase analysis indicates that the as-prepared samples possess a pure skutterudite structure without obvious impurity phases. Microstructural observations demonstrate that S/Se co-filling can effectively regulate the grain morphology and the evolution of grain size. Electrical transport measurements reveal that Fe substitution successfully induces p-type conductivity and optimizes the carrier transport behavior. Meanwhile, S/Se co-filling introduces strong phonon scattering, which significantly reduces the lattice thermal conductivity. For the optimal S$_{0.075}$Se$_{0.025}$Fe$_{0.2}$Co$_{3.8}$Sb$_{12}$, fitting based on the Debye-Callaway model confirms that the resonant frequencies of S and Se are 43.96 cm$^{-1}$ and 35 cm$^{-1}$, respectively. Finally, the S$_{0.075}$Se$_{0.025}$Fe$_{0.2}$Co$_{3.8}$Sb$_{12}$ sample achieves a maximum $zT$ value of approximately 0.22 at 673.15 K. This study provides a feasible strategy for constructing electronegative element co-filled p-type skutterudites and deepens the understanding of multiscale phonon scattering mechanisms in thermoelectric materials.

Key words: S/Se co-filling, skutterudites, thermoelectric materials, high-temperature and high-pressure